The overall objectives of this research project are: (1) To develop new methods for the treatment of cholesterol cholelithiasis by investigating the efficacy and safety of ursic in comparison to those of chenic in the dissolution of gallstones in vivo. (2) To characterize the mechanism of the therapeutic action of ursic, in comparison to that of chenic, by studying the effects of these two bile acids on the solubility of cholesterol in bile and bile acid metabolism. (3) To define the influence of intestinal bacteria upon the metabolism of ursic and chenic in man. (4) To determine the role of caloric intake upon the potential of bile to form or dissolve gallstones in man. (5) To study the relation between deoxycholic acid content and cholesterol saturation of bile. (6) To determine the incidence and types of disturbances of bile acid metabolism in ileitis. (7) To study the mechanism of diarrhea in different conditions of bile acid malabsorption. Specifically this application includes the following proposals: 1) double blind controlled treatment trial of ursic; 2) Study of effects of ursic treatment on composition of biliary lipids (lithogenic index) and bile acid kinetics; 3) study of the pathway and site of the interconversion between chenic and ursic, using labeled chenic and ursic; 4) study of the role of deoxycholic acid formation in supersaturation of bile in Crohn's disease; 5) study of the role of intracolonic pH in the mechanism of diarrhea in bile acid malabsorption.